Acyclicity and Coherence in Multiplicative Exponential Linear Logic

We give a geometric condition that characterizes MELL proof structures whose interpretation is a clique in non-uniform coherent spaces: visible acyclicity. We define the visible paths and we prove that the proof structures which have no visible cycles are exactly those whose interpretation is a clique. It turns out that visible acyclicity has also nice computational properties, especially it is stable under cut reduction.